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QQC Q-Swap Power Bank Tear-Down

Do Touch This

Once gutted, we can see both the top and bottom covers’ LED holes and small pieces of EMI gasket (tubes of metalized fabric stuffed with spongy material) in mirrored corners. The battery status LED is activated by proximity sensing, and those pads are responsible for increasing the touch feature’s sensitivity. It's a simple, yet effective touch. Of course, this is also one more manufacturing step driving cost up.


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The Q-Cell Cells

With the right lighting, camera angle, and some editing to increase contrast, we can barely see the Sanyo brand embossed into the cells’ sleeves. If you were about to point out that this contradicts the packaging’s claim of Panasonic cells, Sanyo has been a wholly owned Panasonic subsidiary since 2011. At QQC’s asking price for its Q-Swap kit, we wouldn't tolerate anything less than top-tier cells.


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Q-Cell Electronics

What lies at the heart of QQC's Q-Swap batteries? A Texas Instrument MSP430 micro-controller in 16QFN packaging runs the show with the assistance of several support components carrying those obnoxious and often undecypherable shorthand codes.

What is an MSP430? Simply, a micro-power 16-bit processor running at up to 16 MHz with proximity sensing features, 2KB of internal flash memory, 128 bytes of RAM, and a 10-bit analog-digital converter for the 2231 (top of its range) variant used here. While this may sound laughable by PC standards, it is strangely overkill for such a simple application.


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Q-Cell Soldering

The soldering quality is generally good, though solder joint appearance is somewhat inconsistent between components, and even between the pads/pins of the same component on account of having slightly too much solder. Instead of slightly concave fillets from PCB pad edges to component contacts, the excess solder has a tendency to ball up on the affected joints. This is most evident around the QFN chip pictured here.

With that said, I’d rather have slightly too much solder, which may not look pretty under high magnification but is otherwise harmless, than being short by any amount and have a much higher likelihood of mechanically weak or intermittent connections.


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Q-Cell Contact, Inside Story

The Q-Cell’s contact slabs are soldered directly to the back of the board. As is common with battery packs, the first and last contacts are indeed battery (pack) negative and positive, while the pads designated D_P and D_N make it look like some form of differential signaling may be going on between the cell and frame.

In the bottom-right corner of the board, you can see the wire connecting the board to the cells’ negative terminal. Although you may not be able to tell at this picture’s resolution, the wire got tinned with just enough solder that the strands’ shape still shows through. We don't see perfect tinning like that very often. Of course, one sample isn’t enough to know whether this is a lucky accident or the norm.


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Q-Cell Charging Board

What do we find on that little charging board? It looks like a typical Li-ion charger arrangement. Starting from the cells’ negative terminals spot-welded to a metal strip on the left then soldered to the board, there is what appears to be a disconnect FET in leadless SO-8 packaging, a smaller control chip to the right with its handful of passive components to set limits, one “large” ceramic capacitor for the hidden switching regulator’s output, and its two tiny inductors that must be connected in parallel to handle 2.1A, as their wiring is approximately 0.18mm in diameter, or AWG #33.

To use such small filter components, the switching regulator’s operating frequency must lie somewhere beyond 1 MHz.


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Sensing Curiosity

As is customary with lithium cells in responsibly-designed devices, a temperature sensor connected to the main board is tucked away and taped between cells. I would have expected this sensor to tie into the charger board instead, since monitoring temperature is more critical during charging to detect an overcharged or failing cell before something unpleasant happen. Good cells seldom fail during discharge unless they are grossly overloaded long enough to overheat. That shouldn't happen here, so long as the Q-Cell has sane current limits.

At first, I thought the white wire might be an enable signal for the controller to shut down the charger on overheat. One quick measurement revealed that it is simply a 5V USB feed for the main board.


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Under The Q-Cell Charger Board

Seeing how power from the micro-B connector went straight to the narrow board between the two cells with no semiconductor in the immediate area, I desoldered one end of the board to have a peek at what lurked beneath.

Predictably enough, the only things hidden under there are two more ceramic capacitors at the input and a Li-ion switching charging controller. According to the only info sheet I could find about it, the ηETA6003 is capable of handling charging currents up to 2.5A at up to 95% efficiency and switching frequencies up to 3 MHz.

To help the tiny regulator cope with waste heat, a wedge of thermal pad material fills the gap between the two cells to help the chip leverage its cells as heat sinks.


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Charging Current

When I first charged the unassembled Q-Cell, I noticed the charging current rapidly dropping from 2.1A to 1.6A as its inductors became unbearably hot. Tapping my fingers on the inductors to cool them down caused the charging current to momentarily rise back to 2.1A. Charging the factory-new sealed cells produced a drop all the way to 1.3A from the same initial 2.1A shown here, albeit without the Q-Cell’s case developing any noticeable hot spot.

Since tap heat-sinking the bare inductors had such an immediate and significant effect on charging current, I suspect QQC could have used inductors with bifilar wiring to reduce I2R and skin effect losses.


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Q-Boost Frame

Did the name inspire the shape or did the shape inspire the name? Either way, if you were still wondering how Q-Swap relates to the actual product, I believe this image is self-explanatory.

The thin Q-Boost frame has a pair of tiny tabs on its long walls that lock onto Q-Cells with a satisfying click and hold them with a reasonable amount of force. The fit between the frame and cell is quite snug, which is necessary for the cell to make good contact with the frame’s pads at the bottom. On the other side of the contact area, we have the type-A socket opening sideways from the Q’s tail.

With no cell inserted, the long walls feel flimsy. Insert a battery, though, as I presume these are intended to be carried, and they may survive being accidentally sat on sideways.


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Daniel Sauvageau is a Contributing Writer for Tom's Hardware US. He’s known for his feature tear-downs of components and peripherals.